There are 2 player and 3 player adventures. The 2nd or 3rd spot in them are called lootspots.
You can either call in a friend or 2 to help you with the adventure while doing it or you can do almost all of it on your own then sell the 2nd and/or 3rd spot to someone (for gc or other resource), let the person kill at least 1 enemy unit then quickly finish the adventure.
It will give you same experience (few 2-20 xp points less) and exactly same loot as on your own, and to the lootspoters it will only give the loot.